Sheet handlers with registration systems are well known. Generally, the sheet handlers have a defined path through which the sheet-like material is transported from one station to another. Registration of documents in such paths is commonly accomplished by driving the sheet-like material to a registered condition against a registration edge. Common means for applying the driving force to move the sheet-like material to the registration edge include cross-rollers, a pinch roller, an angle ball on a belt or any other similar well known device. This particular invention is concerned with cross-rollers.
Sheet handlers are often employed to automatically transport sheet-like material, e.g., documents, copy sheets and the like, to and from processing stations in image processing devices, such as image input terminals and printers. Sheet handlers, often for effectiveness, register the sheet-like material during transport thereof. Registration of the sheet-like material in such image processing devices permits accurate, repeatable and, thus, acceptable functioning of such devices.
Sheet handlers used with an image input terminal transport an image bearing sheet-like material, commonly called a document, to an imaging station for recording the image into or onto another medium, e.g., electronic medium, an imaging surface, such as a photoconductive surface and the like. Document handlers used with these terminals have document registration document means so that documents are presented for imaging in a registered form. Failure to register the document in such systems result in a skewed image being recorded.
Sheet handlers are often used in printers to transport sheet-like material such as cut sheets from a holding tray to an imprinting station where the cut sheets have an image recorded thereon. Again, registration means are provided in many printers, as failure to present a registered sheet to the imprinting station often results in a skewed image formed on the sheet and even missing portions of the image. Also, in printers other processing stations such as stapling stations, binding stations, etc. are often provided and registration means in the sheet handler are provided to deliver registered sheet-like material there too.
Sheet handlers generally have a sheet path through which the sheet-like material travels. Actuation of the sheet-like material is often accomplished through roller sets in which one of the sets is driven. Registration of documents, previously mentioned, can be accomplished through the use of cross-rollers.
In cross-roller devices, the rollers generally contact each other in the sheet path at a nip through which the sheet-like material passes. The rollers are arranged to have a normal force between them and, thus, provide a lateral force on the sheet-like material passing through the nip. The cross-rollers are skewed to the direction of travel of the sheet-like material in the path to urge sheet-like material passing between the rollers laterally against a registration edge and normally along the path. That is at some skew angle bisecting the path direction and the lateral direction.
Optimally, the lateral force on the sheet-like material provided by the cross-rollers is sufficient to move the document to and against the registration edge but is insufficient to buckle the sheet-like material upon engagement. That is, the edge of the sheet-like material upon engagement with the registration edge slides along the registration edge, as it slips in the rollers in the lateral direction. In present systems, the normal force, coefficient of friction and skew orientation of the rollers determine the lateral force applied to the sheet-like materials passing therebetween. The beam strength of the sheet-like material in combination with the force applied to direct the sheet-like material determines whether the material moves to engage the registration edge and whether the material buckles upon engagement with the registration edge. Thus, there exists a need to provide a relatively simple, inexpensive and reliable means for remotely adjusting the normal force in cross-roll registration devices in sheet handlers.
The following disclosures may be relevant to various aspects of the present invention:
U.S. Pat. No. 4,257,587; Inventor: Smith; Filed: Mar. 24, 1981 PA1 U.S. Pat. No. 4,322,160; Patentee: Kobus; Issued: Mar. 30, 1982 PA1 U.S. Pat. No. 4,432,541; Patentee: Clark et al.; Issued: Feb. 21, 1984 PA1 U.S. Pat. No. 4,579,444; Inventor: Pinckney et al.; Filed: Apr. 1, 1986 PA1 U.S. Pat. No. 4,744,555; Inventor: Naramore et al.; Filed: May 17, 1988 PA1 Publication: Xerox Disclosure Journal; Author: Thomas W. Taylor, et al.; Issue: Vol. 7, No. 6, November/December 1982 PA1 Publication: Xerox Disclosure Journal; Author: Vinod K. Agarwal; Issue: Vol. 15, No. 6, November/December 1990; Published: Dec. 22, 1990
The relevant portions of the foregoing references may be summarized as follows:
U.S. Pat. No. 4,257,587 discloses a document registration and feeding apparatus for moving a document allowing a predetermined path and moving the document to a registration edge. The motive force is a deformable scuffer wheel mounted in a flexible drive shaft so that the force applied to documents are limited thereby.
U.S. Pat. No. 4,322,160 discloses a force limiting device used in registering documents on a platen in a document handler. The platen is lowered to expose a registration edge which engages a document adhering to a friction belt to align it for imaging. The platen is raised and lowered by a motor which in combination with the movement of the platen away from the belt adjusts the driving force on the document.
U.S. Pat. No. 4,432,541 discloses an apparatus consisting of a drive roll that is skewed in the direction away from the fixed side edge guide driving an idler roll that is skewed at a greater angle toward the side edge guide whereby when the sheet moves between the drive roll and the guide roll it is laterally driven by the small idler roller to the edge guide and due to the greater coefficient of friction of the idler roller is held against the edge as it is driven forward by the drive roll. The skewing of the drive roll is provided to reduce the chance of damage to the sheet as it is laterally driven by the idler roller.
U.S. Pat. No. 4,579,444 discloses a document side edge registration and deskewing means which includes mated, skewed drive and idler rollers. Take away rollers are also provided in the document path to direct the document sheet through a series of guides. The document enters the nip between the drive and idler roller and the take away rollers are then removed to allow the document to be directed to the registration edge.
U.S. Pat. No. 4,744,555 discloses an idler roller pair mounted on a common shaft and spaced from one another to define a gap therebetween. The idler roller pairs are positioned in conjunction with a drive roller so that the drive roller occupies the space between the idler rollers. The idler roller pairs are skewed so that the longitudinal axis of the respective drive shafts is at a transverse angle with respect to the registration edge mounted on the side of a tray. As a sheet passes through the gap between the drive roller and its pair of idler rollers, it is urged to the registration edge whereupon it continues in the sheet feed direction. The normal force is self limiting, as deformation of the document at the drive wheel limits the normal force according to characteristics of the document. Thus, upon engagement with the registration edge, the document slips under the force in the engagement direction, but continues to advance in the forward direction.
Volume 7, No. 6, pages 371-372 of the Xerox Disclosure Journal discloses a ski-like member which is mounted to a scuffer wheel to effect registration of a document. The scuffer wheel is so mounted to the ski-like member that buckling of the document reduces the force applied by the scuffer wheel to the document.
Volume 15, No. 6 page 473 of the Xerox Disclosure Journal discloses that copy sheet side registration is important and commonly achieved by crossed-rolls. The article states that "An improved crossed-rolls side registration system may be accomplished by automatically adjusting the angle between the driver of the crossed-rolls and the registration edge using for example a small motor or adjusting the normal force between the driver and the idler, or both." The article further states that "a further extension of the improvement would be to automate sensed information with a machine stored look-up table and automatically adjusting the crossed-rolls and registration edge angle or normal force, or both for optimum performance."
Further, there are references which show variable nip or normal force in retard separator/feeders, including belts and roller feeders. Among these references are U.S. Pat. Nos. 4,750,727 and 4,750,726 which disclose apparatus for increasing feeder force applied to a stack of sheet-like material until feeding of a single sheet occurs. Similar, disclosures are found in U.S. Pat. Nos. 4,561,644, 4,475,732, 5,056,604, and 4,368,881 and art cited therein, as well as U.S. Ser. No. 07/767,456.
All of the above described patents, applications and references suffer, as stated above, from various deficiencies. But, specifically, they either fail to teach or fail to provide a means able to compensate to handle a wide range of paper and other materials used in image processing devices including image input terminals, printers and copiers.
That is, a significant disadvantage of these systems is the potential damage to sheets as a result of the fixed or relatively fixed driving force which in the case of lighter weight sheets is in excess of the force necessary to buckle the sheet upon engagement with the registration edge. There is also, in the case of heavier weight sheets, the increase jamming of documents in the path or faulty imaging of sheets as a result of the fixed or relative fixed driving forces which are insufficient to drive the sheet to the registration guide. Thus, for particularly light weight sheets buckling often occurs, while with relatively thick, inflexible sheet material the systems fail to drive the sheet to the registration edge, as expected. In this case, jamming or other errors often result, such as a recording or printing a skewed or off-document image.
In accordance with one aspect of the present invention, there is provided an apparatus for registering a sheet during the movement thereof. The apparatus includes a set of cross rollers. Means are provided to adjust the normal force between the cross rollers. The set of rollers are positioned to accept sheets therebetween and to urge sheets passing therethrough both forward along a path as well as laterally toward a registration edge. The lateral movement of the sheet causes the edge of the sheet to engage a registration edge to align the document according to a predetermined path. The lateral movement of the sheet ceases upon engagement and alignment as the normal force selectively applied to the sheet is less than than the force necessary to buckle the sheet but greater than the force necessary to impart lateral motion to the sheet. Thus, upon registration the sheet begins to slip in the rollers in the lateral direction while still being moved in the path or process direction.
Pursuant to another aspect of the present invention, there is provided a relatively simple, active registration means which includes cross-rollers and a registration edge. The normal force between the rolls is adjusted according to sense signals indicative of the nature and quality of the documents or sheets directed between the cross rolls. The sense signals can be part of the user interface with the particular device or may be generated by detectors and delivered to an operator interface or directly to a control unit. The adjustment of the rollers includes an actuator which adjusts the loading force on the rollers. The actuator can be a manual lever used by the operator to adjust the normal force or motive units such as a solenoid or stepper motor. The motive units can be interconnected with the control unit of the sheet handler of the device with which the present invention is associated to provide for automated adjustments. An operator selection and override can be provided on a user interface panel. Thus, the present invention provides a relatively simple, inexpensive and effective registration means which accepts a wide range of sheet like material. Further, the invention by adjusting the force driving the sheet-like material to compensate for various sizes will also increase the useful life of registration edges by reducing the erosion thereof.